Froth flotation treatment of low grade magnesite ores



I other constituents of the Patented Nov. 21, 1944 FROTH FLOTATION TREATMENT LOW GRADE MAGNESITE ORES Arthur J. Weinig, Golden, (3010., assignor to Basic Magnesium, Incorporated, Las Vegas, Nev., a corporation of Nevada No Drawing. Application February 6, 1943,

Serial No. 474,982

14 Claims.

This invention relates to froth flotation treatments of magriesite ores for the recovery of the magnesite content of such ores.

The present application contains subject matter related to the disclosures in my copending applications, Serial No. 394,851, filed May 23, 1941, for Separation of magnesite ore constituents; Serial No. 430,619, filed February 12, 1942, for Treatment of magnesite ores; Serial No. 458,323, filed September 14, 1942, for Flotation of magnesite; and Serial No. 484,633, filed April 26, 1943, for Magnesite ore treatments. Features described but not claimed herein have been .made the subjects matter of claims in my aforesaid-applications.

Magnesite ores are magnesium carbonate compositions containing also dolomite, forsterite, serpentine and hydromagnesite, constituting contaminants. Such ores occur in a variety of places of which the Luning, Nevada, deposit is typical.

In the present consideration, these ores are classified according to their magnesium oxide content, lime content and insoluble content. A product to be considered of suitable market grade should contain not in excess of 2% CaO-and not to exceed 2% insoluble matter. 1

Where such ores are of relatively high grade the treatment methods heretofore developed will provide an adequate treatment for reducing the lime and insoluble content within prescribed limits at nominal cost. But when the ores are of relatively low grade such methods are not always effective in so reducing the lime and insoluble content, except with an undue amount of treatment, 7

It is an object of the present invention to provide a froth flotation separation of high grade 'magnesite from dolomite and low grade magnesite constituents of a magnesite ore.

Another object of the invention is to provide a combination of ingredients functioning as the reagent in a froth flotation treatment of magnesite ore which is capable of effecting a clean separation ofthe magnesite content from the ore.

A further object of the invention is to provide a simple, eflicient and economical treatment for the separation and recovery content of magnesite ores.

Other objects reside in novel steps and treatments, all of which will appear fully in the course of the following description,

The low grade ores the present invention is designed to treat are much more complex than of the magnesite a. simple association of magnesite and dolomite with minor amounts of silicates. These ores contain a considerable amount of magnesite in a.

relatively pure state, but much of the magnesite content also contains Widely variable amounts of of the flotation separation. Therefore, the real problem of the flotation treatment is to separate high grade magnesite from dolomite and low grade magnesite.

In performing the treatment, the ore is first ground to a suitable degree of fineness and in the subsequent reports of test operations, the ore has been ground to 100 mesh, which may be taken as a standard.

The ore, either during or 'after grinding, is mixed with water to form a free-flowing pulp and a dilution of 4 parts water to 1 part ore will in pounds reagent per ton of ore comprises:

' Lbs./ton Aluminum sulfate 3 to 16 Tetrasodium pyrophosphate 0.5 to 3 Starch 0.3 to '2 Naphthenic acids 0.3 to 2 sacrifice of weight recovery. Some reduction in lime content also results from inclusion of starch serve as a standard for such step. The pulp then is ready for the introduction of the reagent preparatory to performing the froth flotation treatment.

The preferred reagent combination designated In numerous tests it was discovered that the presenceof aluminum sulfate, or an equivalent, is essential in the operation as the other reagent ingredients have only slight effect in the flotation reaction unless such a salt is present. These salts may be classed by their function in the treatment as non-acid hydrogel-forming salts or metallic salts capable of being reacted with an alkali to form a hydroxide hydrogel. Starch, or its equivalent, is particularly effective in lowering the insoluble content of the froth without in the reagent composition.

Tetrasodium pyrophosphate, or-its equivalent, lowers the lime content of the froth for a given weight recovery. When the pyrophosphate and starch are combined in the reagent, the weight recovery exceeds that attained through the use of starch alone, or with the pyrophosphate alone.

When the aforesaid reagent combination is used and the pulp subjected to aeration, a froth forms in which a substantial proportion of the pure magnesite content collects, although low grade magnesite together with dolomite and other contaminants is eiTectively. rejected and passes from I the treatment as a tailings product.

With higher grade ores a. variety of substitute materials may be employed. For example, other I be used.

The froth flotation operation may be performed in any suitable apparatus for such process, al-. though flotation apparatus of the mechanical agitation type usually will be preferred.

- Having thus described the operation of the process of the present invention in a general way, certain typical examples of the treatment of such ores will be cited, particularly to illustrate the cumulative effect of the reagent ingredients.

The following results were obtained:

Test

U. 0.ref.naphthenlcacidJh/tom- 0.5 1.0 1.25 1.30 2.0

Per cent recovery 28 36 43 46 50 Cone.:

Ins 0.34 0.40 0.40 0.08

00.0 ass 5.93 5.03 5.98

The results of the'above tests indicated a recovery of -40% of concentrate containing 1.50% CaO. In order to determine whether variL.

ations in the amounts of reagents used would be of benefit in treating this high-lime ore, a series of tests were made in which first the p'yrophos-- phate was varied with other reagents constant, and then the starch was varied with the other reagents held constant. 8.0 lb. per ton of Ajax aluminum sulphate and 1.25 lb./ton of U. 0. refined naphthenic acid, with a pulp temperature of 100'F. were used throughout. 1.0 lb. per ton of pyropl'iosphate was used when the starch was varied, and 0.5 lb. per ton of caustic pearl starch was used when the pyrophosphate was varied. The results obtained are tabulated as follows:

A. Pyroplwsphate (Pg/r0.) varied I Examples 35 Concentrate Pyro., Per cent Comparing the add1t1on of a partially causlb./ton recovery 11ml C ticized starch; This ore was difiicult to treat 5 using aluminum sulfate, pyrophosphate and 0 5 47 0 64 3 27 naphthenic acids alone where a concentrate grade 40 1:0 43 0:49 v2101 containing 1.50% 02.0 or less was obtained with difiiculties. Reagent additions are stated in pounds reagent per ton of ore treated.

A Percent Est; Reagents otation rem lnsol. CaO MgO per cent magnesite 81 aluminum sulfate o Froth conc 42 0.87 1.91 45.4 03 are rrangement b 58 w w B Per cent 7 Flotation insol. 00.0 M 0 7 cent Reagents rec. 3 g gg 2 gs siumm msu1rate th e aso mm o 56 1.1.. 8.3.1.... it? t it is 0.8 lb. naphthenic acids Degree of grinding of the ore, dilution, temper- 3. Starch varied ature and time of flotation were the same in each case. I

The head ore analyzed 2.42% insol., 4.50% CaO, starch Commits percent MgO 42.4. Estimated magnesite 82%. 10.13011 32%..

XX-35 Ores-A series of tests were made on mi- Inwl- C30 nus 100 mesh XX-35 ore to obtain data for standard grade-recovery curves with'the present combi- -g g 8-2 nation of reagents. The following reagents were 210 31 0154 1101 used: Ajax aluminum sulphate lb./ton 8.0 Causticized pearl starch lb./ton 0.5 The above data show the efliect otvarying the Pyrophosphate -4. .lb./ton 1.0 amount of pyrophosphate, bothas to grade and U. 0. ref. naphthenic acid Variable recovery and the effect of varying the amount of Pulp teniperature degrees 100 caustic starch. In general, it may be said that benefit.

the higher lime ores will require more pyrophosphate; apparently when caustic starch is present the drop in recovery with large amounts of pyrophosphate is not serious. When these results are plotted, the caustic starch curves substantiate generally the observation that variations in this reagent do not have much effect on either grade or recovery, although here again an increase to 1.0 lb. per ton was of considerable Miscellaneous tests Two testswere made on X ore to show the effect of caustic pearl starch on grade of concentrate. The following results were obtained.

These tests showed. a 64% reduction of lime content of concentrates by the addition of 0.5 lb. per ton of causticized starch.

In another instance it was noted that sodium ligninsulphonate (103-N) from the Marathon Chemical Company had slightly improved results when used with a standard combination of reagents. In further work with 103-N, a neutral sodium ligninsulphonate from this company, it was observed that this, product had an effect similar to pyrophosphate when used with caustic starch. Comparative tests on XX-35 ore, using 8.0 lb. per ton of Ajax aluminum sulphate, 1.0 lb. per-ton of causticized pearl starch, 1.0 lb. per ton either of pyrophosphate or 103-N and 0.45 cc. of U. 0. naphthenic acid at 100 F, ave the following results:

P t Concentrate er cen Reagent recovery Insol. CaO

Pyrgphosphaten 36 0. 55 2. 11 103- 38 0. 51 2. 30

These results indicated that the sodium ligninsulphonate was nearly as eifective as pyrophosphate. Froths obtained with the lignin product were much better than those obtained when pyrophosphate was used.

The following tests show the influence of the flotation reagents step by step:

Head ore 3.32% ins'oL; 6.60% CaO Grinding 100 mesh Dilution of flotation-4 parts water to 1 of ore.

ES? g igsg Pet Products Insol. CaO

J 0.651b. naphthenic acids Froth 86% wt 2. 52 6. 60 Tail 14% 7. 20 7. 03 K 0.65 lb. naphthenic acids. Froth 78% wt.-. 1. 60 5. 29 8 lbs. aluminum sulfate Tail 22% wt 9. 52 10.66 L 0.65 lb. naphthenic acids- Froth 62% wt.-. 1. 3. 70 8 lbs. aluminum sulfate Tail 38% wt... 5. 76 10. 80 1 lb. tetrasodlum pyrophosphate.

M' 0.651b. naphthenic acids. Froth 36% wt... 0. 46 1. 35 8 lbs. aluminum sulfate. Tail 64% wt. 4. 70 9. 50 1 lb. tetrasodium pyro- 1 phosphate. 0.5 lb. causticized starch- 'I'heforegoing tests demonstrate that the several ingredients constituting the reagent have a modifying action on one another and with a high lime ore the preferred reagent combination hereinbefore described is particularly suited for selectively floating high grade magnesite in an operation in which dolomite and low grade magnesite are rejected.

Where the terms naphthenic acid and "naphthenic acid compositions are used inthe specification, they are intended to apply to both synthetic or naturally-occurring products of petroleum which in chemical classification are.

designated as any one or combination of non benzenoid cyclic carboxylic acidsderived from petroleum. The range of compositions constituting this group has been tested and found satisfactory for the purposes of the present invention.

In particular, the class of compositions having the formula CnHZn-ZCOOH, consisting chiefly of cyclopentane carboxylic acids have been particularly eflicacious in the treatment, and the various members of these groups may be selected for performing the present invention according results as indicating that any of the compositions coming within the scope of. the aforesaid definition will give comparable results. In all the aforesaid tests, the specified reagent additions refer to pounds of reagent per ton of ore treated.

This condition is due, in part at least, to the.

presence of a non-acid hydrogel-forming salt in the treatment. Such salts have been found to possess a special affinity for calcite, dolomite and similar calcareous materials, but have no aflinity for magnesite. The reaction with the calcareous constituents apparently proceeds according to the following equation:

As a consequence of this reaction, the surfaces of the calcareous constituents are coated by the reaction product rendering them inert to the action of the naphthenic acid collector. From this, it will be apparent thatwher e a given magnesite particle contains a substantial amount 0f dolomite, the resultingreaction on the surface of the calcareous portion is sufficient to prevent flotation of such particle.

For this reason, only high. grade magnesite is floated by the naphthenic acid collector, and as a result, the lime and insoluble content of the concentrate is held well within the prescribed limits.

In detailing the various reagent materials that may be used as substitutes, it should be understood that with respect to the aforementioned hydrogel formation, aluminum sulfate has proved to be a superior reagent in the treatment However, when the lime and silica content of an ore is not excessively high, other salts of aluminum and iron may be substituted for the aluminum sulfate, if desired, and will function in a corresponding manner in the treatment.

With respect to the other reagent compositions, the various materials enumerated as substitutes function substantially as equivalents under various conditions, and their use in a given treatment may be determined largely by availability and cost. Consequently, changes and modifications may be availed of within the spirit and scope of the invention as defined in the hereunto appended claims.

What I claim and desire to secure by-Letters Patent is:

' acid derived from petroleum.

2. A process according to claim 1, in which I the aluminum sulfate content of the reagent is from '3 to 16 pounds per ton of ore treated.

3. A process according to claim 1, in which the tetrasodium pyrophosphate content of the reagent is from 0.5 to 3 pounds per ton of ore treated.

4. A process according to claim 1, in which the starch content of the reagent is from 0.3 to 2 pounds per ton of ore treated.

5. A process according to claim 1, in which the naphthenic acidcomposition content of the reagent is from 0.3 to 2 pounds per ton of ore treated.

6. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite, dolomite, and low grade magnesite particles, and

floating' the high grade magnesite selectivelyaway from the dolomite and low grade magnesite content of the pulp by aerating said pulp in the presence of a reagent composition containing 3 to 16 pounds aluminum sulfate, 0.5 to 3 pounds tetrasodium pyrophosphate, 0.3 to '2 pounds starch and 0.3 to 2 pounds of a nonbenzenoid cyclic carboxylic acid per ton of ore treated.

'7. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said pulp in the presence of a hydrogel-forming salt selected from the group consisting of the salts of aluminum and iron, a lime depressant selected from the group consisting of tetrasodium pyrophosphate and sodium ligninsulfonate, a depressant for the insolubles selected from the group consisting of starch, glues, caramel and caustic extracts of coal, and a collector reagent selected from the group consisting of naphthenic acids, lauric acid and cottonseed fatty acids.

8. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high, grade.

magnesite selectively away from such lime and insoluble content'of the pulp by aerating said pressant for the insolubles selected from the groupconsisting of starch, glues, caramel and caustic extracts of coal, and a naphthenic acid collector reagent.

9. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said pulp in the presence of a hydrogel-forming salt selected from the group consisting of the salts of aluminum and iron, a lime depressant selected from the group consisting of tetrasodium pyrophosphate and sodium ligninsulfonate, a depressant for the insolubles selected from the group consisting of starch, glues, caramel and caustic extracts of coal, and a lauric acid collector reagent. 7

10. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said pulp in the presence of a hydrogel-forming salt selected from the group consisting of the salts of aluminum and iron, a lime depressant selected from the group consisting of a tetrasodium pyrophosphate and sodium ligninsulfonate, a depressant for the insolubles selected from the group consisting of starch, glues, caramel and caustic extracts of coal, and a cottonseed fatty acid collector reagent.

11. The process of treating magnesite-ores by froth flotation, which comprises forming a 'magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said pulp in the presence of an aluminum salt, a lime depressant selected from the group consisting of tetrasodium pyrophosphate and sodium ligninsulfonate, a depressant for insolubles selected from the group consisting of starch, glues, caramel and caustic extracts of coal, and a collector reagent selected from the group consisting of naphthenic acids, lauric acid and cottonseed fatty acid.

12. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and pulp in the presence of a hydrogel-forming salt insoluble content of the pulp by aerating said pulp in the presence of an iron salt, a lime depressant selected from the group consisting of. tetrasodium pyrophosphate and sodium ligninsulfonate, a depressant for insolubles selected from the group consisting of starch, glues, caramel and caustic extracts of coal, and a collector reagent selected from the group consisting of naphthenic acids, lauric acid and cottonseed fatty acids.

13. The process of treating magnesite ores by froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said 14. The process of treating magnesite ores by.

froth flotation, which comprises forming a magnesite ore pulp containing high grade magnesite intermixed with a quantity of lime and insoluble constituent particles, and floating high. grade magnesite selectively away from such lime and insoluble content of the pulp by aerating said pulp in the presence of a hydrogel-forming salt selected from the group consisting of salts of aluminum and iron, alime depressant consisting of a pyrophosphate, a depressant for the insolubles selected from the group consisting of starch, glues, caramel and* caustic extracts of coal, and a collector reagent selected from the group consisting of naphthenic acids, lauric acid and cottonseed fattyacids.

ARTHUR J. WEIN'IG. 

